Shape of the object in our marked point process to detect galaxy groups and clusters in cosmological redshift surveys. Figure shows the cross-section of an axisymmetric object. Object consists of two half-balls connected with a truncated cone (a potato shape). Object is fully determined by its centre position, radius r and shape parameter t  ⩾  1. Shape parameter t gives the aspect ratio of the object along and perpendicular to the line of sight; for t  =  1 the object is a ball. For a given r and t the height of the truncated cone is defined as h  =  2r(t − 1). The shape of the truncated cone is defined by the lines of sights, which are indicated by dashed lines on the figure. The observer is located at far left from the object.